1. Field of the Invention
The present invention relates to a movement stage unit used for moving a sample or positioning it at a predetermined place, and a scanning probe microscope equipped with the movement stage unit.
2. Description of the Related Art
A scanning probe microscope has high resolution capable of measuring or observing fine objects substantially equal to a size of atoms or molecules. In the scanning probe microscope, a measuring and observing section including a detecting section observes a sample like a wafer mounted on a sample stand.
A typical sample stage mechanism used in the conventional scanning probe microscope is shown in FIG. 10, for example. This sample stage mechanism is configured by an X-axis direction stage 901, a Y-axis direction stage 902 and a Z-axis direction stage 903, which are piled up so as to make a triple structure. The sample stage mechanism is placed on a surface table 904. The Z-axis direction stage 904 is equipped with a sample stand 905, on which a sample 906 such as a wafer and the like is mounted. A probe tip 907 for measuring a sample surface is arranged above the sample 906. The probe tip 907 is disposed to a frame fixed on the surface table 905. When each of the X-axis direction stage 901, the Y-axis direction stage 902 and the Z-axis direction stage 903 operates individually, the sample 906 mounted on the sample stand 905 can be moved toward any place. The probe tip 907 scans the surface of the sample 906 based on a change of the relative positional relationship between the sample 906 and the probe tip 907.
For the scanning probe microscope, in general, it is preferable to fail to transmit external vibrations into the sample. Therefore, it is desirable to increase the rigidity of the middle structure from the probe tip 907 to the sample 906. However, in the conventional scanning probe microscope with the sample stage mechanism having the aforementioned triple structure, the entire rigidity of the sample stage mechanism is determined by the structure formed out of combining the X-axis direction stage, the Y-axis direction stage and the Z-axis direction stage in series. This structure of the series combination results in a lowering of the entire rigidity because each rigidity of the three stages are added. Further, since the three stages piled-up structure increases the entire height of the sample stage mechanism, the shape of the frame 908 increases in its size, and therefore the rigidity of the frame 908 is reduced.
As a prior art literature stating the art for increasing the rigidity of the structural section from a detecting section to the sample in the sample stage mechanism of the scanning probe microscope, the publication of Tokko-Hei (Patent) No.1-34746 can be cited. The apparatus stated in the literature is adapted to reduce the structure of movable sections in its size as small as possible and to directly drive the movable sections by driving sections. However, since the driving section in the movable section operates based on the direct driving system and the point end of the driving section has functions of driving and supporting, the apparatus of the prior art poses a problem that the rigidity of the sample stage mechanism is determined by the rigidity of the driving sections. To say concretely, each rigidity of steel balls, floating pads, nut members, feeding screws have an effect on the entire rigidity based on their series relationship. In addition, the structure for the direct driving increases the height of the sample stage mechanism.